JE not only offsets the piston pin, they made it shorter. All JE asymmetrical pistons are designed to use a 2.250-inch wristpin while most other designs require a 2.500-inch or even 2.750-inch pin. Since wristpins are made of steel, a small reduction can make a large difference in overall weight. In most cases, the shorter wristpin reduces weight by around 10 grams per cylinder while also reducing the potential of pin flex and breakage.

This is a graphic representation of the various loads experienced by an LS7 piston referenced by degrees of crank angle. Kalinowski says, "The pin offset has a minimal effect on the side load force that acts upon the piston and is primarily a function of engine geometry, cylinder pressure, crank angle, etc. So in the LS case, there is a fixed major thrust side load and fixed minor thrust side load acting upon the piston based on the calculations. The pin offset does affect the internal piston stress though as it is a structural change."

To optimize skirt profiles for race engines, JE ran tests based around very high cylinder pressure forced-induction applications of more than 1,000 hp. For these LS pistons, they modeled a 4.100-inch stroke, 6.125-inch rod peak-firing-pressure scenario. Here we can see that major thrust load is close to 12,000N (Newtons), while the minor thrust load is barely 3,000N.

After developing an initial asymmetrical design structure in SolidWorks, JE ran the design through several iterations of finite element analysis consisting of multiple thermal and mechanical load cases. This FEA image shows stress on an asymmetrical LS major thrust face and crown.

After several refinements, JE arrived at a final design that showed reduced stress, better heat management, and high horsepower tolerance. This FEA image shows stress on an asymmetrical LS LSX minor thrust face.

JE ran prototypes of the new design in everything from 250hp turbo four-cylinder street cars to 2,000hp turbo drag cars with success. Here we see the contact pressure on the major thrust face.

But the benefits aren't just for power production; the lighter, more balanced design also resulted in a quieter piston that exhibits less slap. This is the contact pressure on the minor thrust face.

JE Pistons
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